THE CARBONIFEROUS PLATEAU. 115 



The form of the plateau can be seen by referring to either of the two 

 maps of the Atlas. In the topographical map it appears as a topographical 

 feature; in the geological it is marked as the great body of the Carbonifer- 

 ous exposure. It attains its high elevation by a gradual slope from the 

 west, from the north, and from the south, while its eastern margin, over- 

 looking the area of the slates, is a more or less bold escarpment or cliff, 

 broken and serrated, however, by the penetration of valleys and streams. 

 It has a width east and west of from fifteen to twenty miles, and a length 

 north and south of sixty miles, covering altogether between nine hundred 

 and one thousand square miles, or about one-sixth of the total area of 

 the Hills. Its surface is generally smooth or gently undulating, but is 

 sharply cut by the draining streams which traverse it in deep and steep- 

 sided cailons. Considered in its total mass it is the greatest elevation of 

 the Hills, and it bears upon its broad back a crag which is second to but 

 one other summit in height. Crook Tower has an altitude above the sea 

 of 7,320 feet, and is only 80 feet lower than Harney Peak, while it over- 

 tops Teriy Peak, the next in elevation, by fully 100 feet. It rises only 

 about 200 feet above the level of the adjacent portions of the plateau. 



Approaching from the west, at the headwaters of Beaver Creek, one 

 ascends from the Red Bed Valley (5,300 feet) by a slope of the Red Beds, 

 more or less gradual, to the general level of the plateau, here about 7,000 

 feet high. This general level, varied only by undulation, extends thence 

 eastward to the margin of the plateau which overlooks the area of the 

 slates. 



From the base of Crook Tower (7,100 feet) the surface of the mesa 

 spreads southward to the region west of Castle Creek and the headwaters 

 of Spring Creek with a level varying little from 7,000 feet. From the 

 headwaters of French Creek, however, there is a visible descent of the 

 plateau toward the south and southwest. Near the head of Red Canon 

 Creek the elevation is about 6,000 feet, and at the southwest the mesa soon 

 ends by the descent of the limestone. 



Northward and northwestward from Crook Tower the Carboniferous 

 rocks extend to the valley of the Redwater in much the same manner as 

 they spread and disappear southward, except that the plateau character of 



